1. Field of the Invention
The subject invention relates to a method and system for determining a voltage in each cell of a plurality of battery cells connected in series.
2. Description of the Related Art
Electric vehicles and hybrid-electric vehicles typically utilize numerous cells (i.e., batteries) for powering electric drive motors and other electric equipment. These cells are often connected together in a series relationship, as is well known to those skilled in the art, to provide higher voltages.
Due to variations between individual cells, such series-connected cells require periodic balancing, i.e., charge equalization, to maintain a steady voltage and prevent premature failure. One difficulty in cell balancing is determining which cell or cells may need to individually charged or replaced. Therefore, it is necessary to provide a system to determine the voltage in each cell.
Numerous systems and techniques have been developed to address this necessity. Prior art systems often utilize one or more capacitors connected to the cells such that a more stable voltage may be measured. A plurality of busses connect the cells to the capacitor. For instance, U.S. Pat. No. 6,362,627 (the '627 patent) to Shimamoto et al. discloses a system with a plurality of cell switches connected to various cells, a pair of busses connected to the cell switches, a capacitor connected to the busses, and an amplifier connected to the capacitor.
Despite the system described above and others existing elsewhere in the prior art, there remains an opportunity for a method and system for measuring voltage of individual cells connected in series having improved accuracy.